AP Biology 2006-2007
“Fighting the Enemy Within”
Immune System
lymphocytes attacking cancer cell
phagocytic leukocyte
lymph system
Regents Biology
Avenues of attack
▪ Points of entry ◆ digestive system ◆ respiratory system ◆ urinary system ◆ genitals ◆ break in skin
Regents Biology
Why an immune system?▪ Attack from the outside & inside
◆ we are a tasty vitamin-packed meal ▪ cells are packages of proteins, carbohydrates & fats ▪ no cell wall
◆ animals must defend themselves against invaders ▪ viruses
⬥ HIV, flu, cold, measles, chicken pox, SARS ▪ bacteria
⬥ pneumonia, meningitis, tuberculosis ▪ fungi
⬥ yeast ▪ protists
⬥ amoeba, Lyme disease, malaria ◆ cancer cells
▪ abnormal body cells
What’s forlunch?!
Regents Biology
How are invaders recognized?▪ Antigens
◆ chemical name tags on the surface of every cell ▪ “self” vs. “invader”
disease-causingbacteria
disease-causingvirus
one of your own cells
antigens say:“I belong here”
antigens say:“I am an invader”
antigens say:“I am an invader”
Regents Biology
Lines of defense▪ 1st line:
◆ broad, external defense ▪ “walls & moats”
◆ skin & mucus membranes ▪ 2nd line:
◆ broad, internal defense ▪ “patrolling soldiers”
◆ phagocyte (eating) WBCs ▪ 3rd line:
◆ specific, acquired immunity ▪ “elite trained units”
◆ lymphocyte WBCs & antibodies ▪ B & T cells
Barriers
Non-specific patrol
Immune system
Regents Biology
1st line: Physical Barriers▪ non-specific defense ▪ external barriers
◆ skin & mucus membranes ◆ excretions
▪ sweat ▪ stomach acid ▪ tears ▪ mucus ▪ saliva
Lining of trachea: ciliated cells & mucus secreting cells
Regents Biology
2nd: Generalist, broad range patrols ▪ Patrolling white blood cells
(macrophages) ◆ attack invaders that get through the skin
▪ recognize invader by reading antigen
Macrophage “eating” bacteria
Regents Biology
Fever ▪ When a local response is not enough
◆ full body response to infection ◆ raises body temperature ◆ higher temperature helps in defense
▪ slows growth of germs ▪ helps macrophages ▪ speeds up repair of tissues
Regents Biology
3rd line: Lymphocytes ▪Specific defense
◆ responds to specific invaders ▪ recognizes specific
foreign antigens ▪white blood cells
⬥B cells & antibodies ⬥T cells
B cell
Regents Biology
B cells & antibodies▪ B cells
◆ white blood cells that attack invaders in blood
◆ mature in Bone marrow ▪ Patrolling B cells
◆ make antibodies against invader immediately ▪ Memory B cells
◆ remembers invader ◆ can make antibodies quickly the next time
▪ protects you from getting disease more than once
Regents Biology
▪ Proteins made by B cells that tag invaders in the blood so macrophages can eat them ◆ tag says “this is an invader” → gotcha!
▪ biological “handcuffs” ◆ antibody attaches to antigen of invader
Antibodies
macrophageeating tagged invaders
invading germs tagged with antibodies Y
Y
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Y
B cells releasing antibodies
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Y Y
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Y
Regents Biology
B cells immune responseinvader (foreign antigen)
Y
Y
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Y
B cellsY
YY
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Y
Y
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YY
YY
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YY
Y
Y
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Y “reserves”memory B cells
Y
Y
Y
Y
Y
YY
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B cellsrelease antibodies patrol blood forever
recognition
10 to 17 days
YY
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YY Y YY
Y
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YYYY
Y
Regents Biology
Vaccinations ▪ Exposure to harmless version of germ
◆ stimulates immune system to produce antibodies to invader
◆ rapid response if future exposure
▪ Most successful against viral diseases
Regents Biology
▪ Vaccinations ◆ advantage ▪ don’t get illness ▪ long term immunity
⬥produce antibodies for life ▪ works against many viruses
& bacteria ◆ disadvantage ▪ not possible against all invaders
▪ Breastfeeding ◆ mother’s milk gives baby
antibodies & keeps baby healthy`
Protecting you from disease
IMPORTANTPROTECTION antibodies pass from mother to baby in breast milk
AP Biology 2006-2007
What if the attacker gets past the B cells in the blood &
infects some of your cells?You need trained assassins to kill off these infected cells!
T
Attack of the Killer T cells!
Regents Biology
T cells▪ T cells mature in Thymus ▪ Helper T cells
◆ sound the alarm for rest of immune system
▪ Killer T cells ◆ destroy infected body cells
Regents Biology
Immune responseinvader
invaders in blood invaders infect cells
B cells T cells
macrophages
helper T cells
patrollingB cells
memoryB cells
memoryT cells
killerT cells
YYY
Y
YY
Y
YantibodiesY
Y
Y
skinskininvaders in body
YY
Y
Y
YY
Y
YantibodiesY
Y
Y
Regents Biology
Diseases of the immune system▪ HIV: Human Immunodeficiency Virus
◆ infects helper T cells ◆ helper T cells can’t activate rest of
immune system ▪ body doesn’t hear the alarm
▪ AIDS:Acquired ImmunoDeficiency Syndrome ◆ immune system is weakened ◆ infections by other diseases ◆ death from other invading
diseases or cancer
Regents Biology
Curing you of disease▪ Antibiotics = medicine
◆ advantage ▪ kill bacteria that have successfully
invaded you ⬥make you well after being sick
◆ disadvantage ▪ use only after sick ▪ only good against bacteria ▪ possible development of
resistance by bacteria (if don’t use correctly)
▪ can get sick again
Regents Biology
Immune system malfunctions▪ Allergies
◆ over-reaction to harmless compounds ▪ allergens
⬥proteins on pollen ⬥proteins from dust
mites ⬥proteins in animal
saliva ▪ body mistakenly
thinks they are attackers
AP Biology 2009-2010
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